Well, I suppose that would seem equivalent if you completely ignored history.
White people have been enforcing white cultural norms by co-opting and covering over existing culture for centuries. Whitewashing roles is just one aspect of that. If you replace a black or Asian part in a production with a white person, that representation is gone. Whiteness is simply too omnipresent to be erased by putting a person of color in the role of a white historical figure. Also, because so few roles are written specifically to allow POC and because on neutral/unspecified roles white people get the role 99 times out of 100, the opportunities for POC in theater, TV, and movies simply aren’t there. We need to let them in. Sometimes that will mean POC playing white historical figures, and that is ok and not equivalent to whitewashing.
Edit to add: this week’s Code Switch podcast is about the paucity of roles for Asians in theater and how that relates to Miss Saigon. It’s worth a listen.